Method for producing a dental shaped part

ABSTRACT

A method for producing a dental shaped part includes checking an outer contour of a tool of machining equipment, using least one gauge provided on a blank formed from a tooth restoration material from which a dental shaped part is to be machined using the machining equipment. The method also includes machining the dental shaped part from the blank using the tool of the machining equipment, when the outer contour of the tool corresponds to the at least one gauge provided on the blank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/557,153, filed Nov. 17, 2005, now U.S. Pat. No. 8,057,912, which is anational-stage entry of International Application No. PCT/EP2004/051398,filed Jul. 7, 2004, and which claims benefit under 35 U.S.C. §119 ofGerman Patent Application No. 103 30 758.3, filed Jul. 7, 2003. Theentire disclosure of each prior application is incorporated by referencein its entirety herein for all purposes

BACKGROUND OF THE INVENTION

The invention relates to a blank as defined in the generic clause ofclaim 1 which is to be used in the production of a dental shaped part,and to a method of producing said shaped part.

EP 0 160 797 discloses a blank for the production of dental shapedparts, which blank is made up of a handle and a corpus of differentmaterials. A reference surface on the handle can be formed in such a waythat control information for the machining process depending on thecharacteristics of the blank, can be derived.

Another blank for the production of dental shaped parts is disclosed byDE 196 12 699. Here again, recognition of the type of blank from thegeometrical shape of its contours is disclosed.

EP 0 455 854 discloses a blank, from which there can be carved a matingpart to be administered to the patient, on the one hand, and anadditional retaining or supporting part, on the other hand. A recess iscarved into the mating part, which is shaped in such a way that it canbe fitted on the retaining or supporting part.

The position of the abrasion-prone tools used for machining the blank isadjusted such that the tools are moved to engage defined referencesurfaces on the blank. These reference surfaces can be on the handle, asshown in EP 0 160 797 or they can, as shown in DE 196 12 699, bepositioned on the corpus of the blank or on its own reference part,which is attached to the blank at more or less arbitrary places.

The reference surfaces that are provided in the prior art are onlysuitable for purposes of adjustment of the tool relative to the blank.

It is an object of the invention to make it possible to reliably analyzeor identify the tool equipment and/or the type and state of wear of thetool used in the machining equipment employed for machining the blank.In particular, it is intended to provide means of recognizing incorrecttool setups in grinding machines using different types of tool at thesame time.

SUMMARY OF THE INVENTION

This object is achieved, according to the invention, by the featuresdefined in the claims, with certain developments being set forth in therespective subclaims.

The advantage of a blank for the fabrication of dental shaped parts,comprising a corpus of tooth restoration material, from which, in turn,the shaped part can be made by machining, with the blank exhibiting atleast one gauge (also referred to herein as “gage”) that isgeometrically formed in such a way that the tool used for machining isidentifiable on the basis of its outer contour by means of the at leastone gage, is that the effectiveness of machining can thus be guaranteedusing the intended specialty tool. Whether the blank consists ofceramics, metal, plastics, or any other dimensionally stable material isof no consequence. An incorrect tool setup can be particularly wellrecognized in the case of grinding machines that use different types oftool at the same time. Both grinding and milling, for example, aresuitable machining processes.

The gage is advantageously assigned to an ideal outer contour of a firsttool, as this makes it possible to identify the tool that corresponds tothe gage. In addition, another tool having a different ideal outercontour from that of the first tool can be distinguished with the aid ofthe same gage. In this way, not only can the tool matching the gage beselected, but different tools can be distinguished from each other.

An advantageous shape of such a gage can be a recess, in which the idealouter contour of the first tool engages. Such engagement can be madepossible, for example, by forming the recess such that the tool havingan ideal outer contour fits it exactly.

Advantageously, the gage exhibits a recess that corresponds to a firstdiameter d1 of the ideal outer contour of a first cylindrical tool,which diameter is smaller than the ideal outer contour of a secondcylindrical tool having a second diameter d2. In this way, at least twotools of identical geometry but of different sizes can be distinguishedfrom each other.

Another advantageous shape of such a recess serving as a gage is arecess that is tapered in correspondence with the ideal outer contour ofa first tapered tool, with the recess tapering to a diameter that issmaller than the smallest diameter of the ideal outer contour of asecond cylindrical tool. In this way, it is also possible to distinguishtools of different geometry from each other. This principle is naturallyalso transferable to any other tool shapes, and can be used, forexample, on tools having a rounded end.

Advantageously, the gage is in the form of a groove or bore, since theseare particularly easy to create.

It is especially advantageous when the gage is designed in such a waythat when the tool to which the gage is assigned is moved into the gage,the actual state of the permissible allowances of the respective toolcan be identified such that the degree of wear of the tool can beassessed and, for example, a certain minimum tool quality can beprescribed. A further advantage is that it is possible to effect areliable analysis or identification of the tool setup and/or the type oftool used in the machining equipment employed for machining the blank,and the wear condition of said tool.

Another advantage is gained when the blank comprises a handle formounting and/or positioning the corpus of the blank in a machiningdevice and when the gage is provided on said handle, since thereby thegage will remain effective throughout the entire machining operation andthe corresponding tools can be checked on a continuous basis. Suchidentification of poor quality tools or incorrect setups will becontributory, for example, to preventing tool fracture during machining.

Alternatively, at least one gage can be on the handle or on the corpusof the blank or on a reference area, by which means special productioncharacteristics can be taken into consideration. In addition, at leastone gage can be at at least two of the said positions.

If the gage is designed as a universal gage for prospective tools,advantageously various tool geometries can be checked with only onegage. A gage is considered to be a universal gage if the geometricalshape of several tools can be checked with the aid of this one gage.This requires that the shape geometry itself consists of severalindividual shape geometries, of which each corresponds to the toolgeometry of its respective tool. By this means, it is not only possiblefor a more extensive tool setup to be examined with the aid of only onegage, but it is also possible to examine the degree of wear of a numberof, or if necessary all, tools with the aid of just one gage. In thisway, it will be possible to detect incorrect setup with minimumelaboration. Instead of using only one universal gage, several universalgages of identical or different geometrical shapes can be used if thiswould seem necessary, for production or control reasons for example, inorder to enable the tool to be driven to the blank more quickly, forinstance.

In accordance with a development, several gages are provided for thecharacterization of a single tool and this single tool can be examinedfor more than one parameter of its condition and in particular for itsdeviation from an ideal condition.

The advantage of a procedure for the fabrication of dental shaped partsusing a blank corpus of dental restoration material, from which theentire shaped part can be carved in a machining device by means of atool, and the profile of the tool selected for such machining isexamined before it is put to use with the aid of at least one of thegages disposed on the blank is that it is possible to ensure, in thisway, that said tool is, indeed, the correct tool for the machiningoperation to be carried out. This is achieved in that the actual valuesobtained are compared with the ideal outer contour.

A further advantage results if the tool dedicated to the gage is driveninto the gage and the current deviation of the assigned tool from theideal is determined, since information about the momentary toolcondition can be determined in this manner each and every time the toolengages the gage(s). This can be done several times during an operationsequence. Thus an optimal condition and, therefore, high quality of theshaped part can be guaranteed.

Another advantage results when the degree of deviation of the actualcondition of the tool from the ideal outer contour of the tool isdetermined and this deviation is allowed for when organizing the controlof the blank machining operation. A parameter, for example, can beestablished for this purpose. A tool whose unsuitable condition has beenrecognized can, in such a case, be excluded from the machining processand new or other tools in better condition can carry out the task inhand. It is also conceivable to reduce down times by causing a change oftool to be suggested only if the machining process cannot be finishedwith any of the other tools that are already involved in the process.The information gained from the comparison can thus be used for a toolcondition-specific control of the machining process.

All in all, it is to be emphasized that the gages can be positionedanywhere and, advantageously, are not only provided for the selection ofthe tool by reproducing the negative shape of the tool intended formachining in its ideal condition, but are also available for determiningthe wear condition of the tool. The exact position of the gage will beknown to the machining equipment or is determined by it.

In addition, the gage can be designed such that it can identify toolsthat are designated for the material.

This can, for example, be effected via the geometry or a specificmachining resistance when using the tool in the known geometry of thegage under known machining effort.

BRIEF DESCRIPTION OF THE DRAWINGS

The method of the invention is described with reference to the drawings,in which:

FIG. 1 a is a perspective view of a first blank for the fabrication of adental shaped part with a gage on a handle of a blank corpus,

FIG. 1 b is a perspective view of a further embodiment of a blankaccording to the invention with a gage on the blank corpus,

FIG. 1 c is a perspective view of a further blank having at least onegage on a reference surface located on the blank,

FIG. 2 a is a longitudinal cross-section of the blank of FIG. 1 a,

FIG. 2 b is a longitudinal cross-section of the blank of FIG. 1 b,

FIG. 2 c is a longitudinal cross-section of the blank of FIG. 1 c,

FIG. 3 a shows a machining tool in the form of a diamond-coatedcylindrical grinder having a first diameter,

FIG. 3 b shows a machining tool in the form of a diamond-coatedcylindrical grinder having a second diameter,

FIG. 3 c shows a machining tool in the form of a diamond-coated grinderhaving a conical point,

FIG. 3 d shows a machining tool in the form of a diamond-coated grinderhaving a tapered portion and a rounded conical point,

FIG. 3 e shows a machining tool in the form of a diamond-coated grindingwheel,

FIG. 4 a shows a gage by means of which the machining tool of FIG. 3 ais checked,

FIG. 4 b shows a gage by means of which the machining tool of FIG. 3 bis checked,

FIG. 4 c shows a gage by means of which the machining tool of FIG. 3 cis checked,

FIG. 4 d shows a gage by means of which the machining tool of FIG. 3 dis checked,

FIG. 4 e shows a gage by means of which the machining tool of FIG. 3 eis checked,

FIG. 4 f shows a gage by means of which the wear condition of themachining tool of FIG. 3 c is checked,

FIG. 5 shows a gage that is designed as a universal gage for checkingseveral tools having various contours,

FIG. 6 shows a further embodiment of a gage suitable for use as auniversal gage, and

FIGS. 7 a, 7 b show wear measurement means for a cylindrical and conicalgrinder respectively.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The blank of FIG. 1 a contains a corpus 1, which can consist of amaterial commonly used in dental technology, e.g. a ceramic material,but also of any other dimensionally stable material such as metal orplastics, from which the shaped part will be fabricated by means of amaterial removal machining process. The corpus 1 of the blank isadvantageously circular or rectangular in cross section. The front endof the corpus of the blank is adjoined by a cylindrical handle 2 inknown manner.

The material of handle 2 can be identical with, or different from, thatof the corpus 1. In the case of different materials, blank corpus 1 willbe fastened to handle 2, for example by gluing. For this purpose, handle2 exhibits, for example, a circular cylindrical flange 2 a having adiameter that is sufficient to ensure secure attachment to corpus 1, anda shaft 2 b for insertion into the machining equipment. Shaft 2 b isdesigned to fit into a predefined socket on the machining equipment.

In FIGS. 1 a to c, a recess 5 having gage properties is provided. Suchrecesses can be provided individually or in moderate numbers at variousplaces of the blank. Due to their gage properties, these recesses serveto select and evaluate the individual tools, since five specific sets ofdata of the tool, e.g. their dimensions, state of wear, and position,can be identified with the aid of the recesses 5.

The blanks illustrated in FIGS. 2 a to 2 c are structurally comparableto the blanks of FIGS. 1 a to 1 c. According to FIG. 2 a, two gages 4, 5are provided on flange 2 a of handle 2 of the blank in the form of gagerecesses. In this case, the gages are in the form of a groove and bore4, 5 respectively. FIG. 2 b shows a blank which exhibits two gages 4, 5on the corpus 1 of the blank. The blank of FIG. 2 c is also structurallycomparable to the blank of FIG. 1 c and comprises a mating part 6, whichin this case is disposed on corpus 1 opposite handle 2. The mating part6 can be of the same material as the corpus of the blank and can belocated on the axis 7 of the handle and can itself serve to determinethe size and position of the machining tool. Alternatively, any numberof other locations can be considered for the mating part 6, as long asit does not impede the machining process. Moreover, it can have thecylindrical shape shown or some other shape. Two gages 4, 5 are disposedon mating part 6 in the form of recesses, which in this figure are inthe form of a groove 4 and bore 5.

With all blanks, it is essential that the position of the gages 4, 5 onthe machining equipment is known or can be unambiguously determined.This can be done, for example, by scanning

FIG. 3 shows machining tools as used for machining corpus 1. FIGS. 3 aand 3 b show a diamond-coated cylindrical grinder or milling cutter,with the grinder 11 of FIG. 3 a exhibiting a first diameter d1 and thegrinder 12 of FIG. 3 b a second diameter d2. A grinder that is designedin this way is primarily used for machining interior spaces withvertical walls. FIGS. 3 c and 3 d each show a diamond-coated grinder 13,14 that tapers to a point. In FIG. 3 c, the end of the grinder 13exhibits an angle α of 45°. In FIG. 3 d the end of the grinder 14 is inthe form of a cone, of which the point is rounded with a radius R. Agrinder that is shaped in this way is primarily used for machiningocclusion surfaces with fissures, as well as interior spaces withnon-vertical walls.

FIG. 3 e shows a diamond-coated grinding wheel 15, which is used forboth separation and roughing as well as for carving down to finaldimensions. The edges of the grinding wheel exhibit a radius r and thewheel has a diameter d5 and a width b.

FIG. 4 shows the machining tool of FIG. 3 engaged in a gage. FIGS. 4 aand 4 b show a diamond-coated cylindrical grinder 11, 12, anddemonstrate how grinder 11 penetrates the bore-shaped gage 5 by adistance t1, whilst the other grinder 12, because of its largerdiameter, cannot penetrate gage 5. The penetration depth t2 is in thiscase equal to zero, from which it can be ascertained that tool 12 isinvolved.

FIGS. 4 c and 4 d each show a diamond-coated grinder 13, 14 tapered to atip as it penetrates gage 5 in the form of a bore. The penetrationsillustrated in FIGS. 4 c and 4 d of a magnitude t3 in FIG. 4 c and t4 inFIG. 4 d, serve not only to determine the ideal outer contour and thusto define the type of tool, but also provide information on the wearcondition and the suitability of the respective tool for the intendedmachining process.

FIG. 4 e shows a diamond-coated grinding wheel 15 at a point at whichgrinding wheel 15 is about to move into the groove-shaped gage 4 of FIG.3 e on corpus 1 of the blank. This moment of penetration providesinformation as to whether the grinding wheel is too thick and thusunsuitable for the scheduled grinding procedure.

FIG. 4 f shows a gage 5 that is used to detect the wear condition of thetool tip. The gage has a conical open region 5.1, which merges into abase region 5.2. Between them is a cylindrical region 5.3. Tool 13, whennew, moves into the gage at its pointed end such that only the tiptouches the base 5.2. If the tip is as worn out as on tool 13′, then thedepth of penetration of its pointed end up to the point of reaching thebase 5.2 or up to the point of touching the side walls of the openregion 5.1 will be greater than when tool 13 is new. The amount of wearcan thus be inferred from this measurement.

FIG. 5 shows a single cylindrical recess 5′ for tools 11 to 14 shown inFIGS. 3 a to 3 d that is designed as a universal gage. The respectiveactual penetration depths t1′, t2′, t3′, t4′, provide information on thecondition of the respective tool and thus on the suitability of the toolfor the intended machining operation.

FIG. 6 shows a further single recess 5″ serving as a universal gage.This recess includes a bore 16 having a diameter d2 and an associatedpossible penetration depth t2 and one having a diameter d1 and anassociated possible penetration depth t2. In addition, the recessexhibits a taper 17 having a cone angle β and a further taper 18 havinga cone angle α for the examination of corresponding tools.Alternatively, instead of one or more angles, one or more roundingshaving radii R (see FIG. 3 d) that match the respective tools can beprovided. The penetration depth achieved in each instance can yieldinformation on the condition of the respective tool and thus thesuitability thereof for the intended machining operation. FIGS. 7 a and7 b show how wear measurement can be carried out. Tool 11 is furnishedwith a coating 19 that provides the actual cutting edges, for examplethe diamond coating of a grinding pin. This coating 19 exhibits an idealouter contour 20, which is indicated by the dashed lines. However, dueto the wear incurred during machining, the actual outer contour 21 oftool 11 will deviate from the ideal outer contour 20.

In the region of the end-cutting surface, the amount of wear of thecoating 19 between the ideal outer contour 20 and the actual outercontour 21 is equal to the distance 6 which, with an original coatingthickness of from 50 to 60 μm, can well amount to from 40 to 50 μm. Thewear of the end-cutting surface can be determined by measuring the depthof penetration of tool 11 into gage 5. FIG. 7 b shows how a gage 5 canbe used for measurement of the wear of a coated conical grinder. Theconical grinder has a coating 19, which again has an ideal outer contour20 and an actual outer contour 21. Due to the bore 16, the diameter ofthe used tool 13 is first identified and, due to a stop limit surface 22having a central bore 23, the wear δ_(d) of the envelope of the cone isdetermined. The wear δ_(s) of the cone tip can be determined inaccordance with FIG. 7 a, but can also be measured in accordance withFIG. 7 b when certain empirical values are available. For themeasurement of a truncated cone point, and also of a conical grinder, aseparate gage can be provided for each diameter, and the wearmeasurement can, in each case, be carried out by measuring the depth ofpenetration into the gage.

What is claimed is:
 1. A method for producing a dental shaped part, themethod comprising: checking an outer contour of at least one tool ofmachining equipment, using at least one gauge provided on a blank formedfrom a tooth restoration material from which a dental shaped part is tobe machined using the machining equipment, wherein the gauge is arecess, and wherein the checking includes: engaging at least part of thetool with the recess at a penetration depth in the recess, thepenetration depth determining at least one of a condition of the tooland an ideal outer contour indicating a type of the tool, and removingthe at least part of the tool from the recess; and machining the dentalshaped part from the blank by using the tool of the machining equipment,checked in the checking, to remove material from the blank, when theouter contour of the tool corresponds to the at least one gauge providedon the blank.
 2. The method as defined in claim 1, wherein the tool ofthe machining equipment is one of a first tool and a second tool, and adiameter of an end of the first tool is smaller than a diameter of anend of the second tool, the recess has at least one predetermineddimension and shape, the end of the first tool fits into the recess, andat least a portion of the recess is smaller in size than the diameter ofthe second tool, said dental shaped part is machined from the blank byusing at least one of the first and second tools to remove material fromthe blank, and the checking includes engaging at least part of at leastone of the first and second tools with the recess at a penetration depthin the recess and removing the at least part of the at least one of thefirst and second tools from the recess, the penetration depthdetermining at least one of a condition of the at least one of the firstand second tools and an ideal outer contour indicating a type of the atleast one of the first and second tools.
 3. The method as defined inclaim 2, wherein the blank has a handle for positioning a corpus of theblank in machining equipment, and the recess is provided on the handle.4. The method as defined in claim 3, wherein the recess is located onthe corpus.
 5. The method as defined in claim 2, wherein the gaugedistinguishes an outer contour of the first tool from an outer contourof the second tool.
 6. The method as defined in claim 2, wherein theshape of the recess is cylindrical and a diameter of the recess issmaller than the diameter of the second tool.
 7. The method as definedin claim 2, wherein the recess is tapered to correspond at least in partto an outer contour of the first tool and the recess tapers to adiameter which is smaller than the diameter of the second tool.
 8. Themethod as defined in claim 2, wherein the recess is in the form of agroove or a bore.
 9. The method as defined in claim 2, wherein therecess identifies a state of permissible allowance of the first toolwhen the first tool engages the recess.
 10. The method as defined inclaim 2, wherein the gauge functions as a universal gauge forprospective tools.
 11. The method as defined in claim 2, wherein thegauge of the blank is one of a plurality of gauges, each of theplurality of gauges being designed as a recess having dimensions and ashape that correspond at least in part to an outer contour of one of thefirst tool or the second tool.
 12. The method as defined in claim 2,wherein the gauge has a first diameter of an outer contour of the firsttool, and an outer contour of the second tool does not fit into thegauge.
 13. The method as defined in claim 1, further comprising: drivingthe tool into the at least one gauge provided on the blank; anddetermining an actual state of a permissible allowance of the tool. 14.The method as defined in claim 13, further comprising: determining adegree of deviation of the actual state of the permissible allowance ofthe tool from an ideal outer contour of the tool; and controlling themachining of the dental shaped part from the blank based on thedetermined degree of deviation.